Darwin's theory or Darwinism
The second theory on the hypothesis of biological evolution is known as Darwinism. Charles Darwin described it in his book The Origin of Species by Natural Selection.
According to Darwinism, change is a process that continues in living beings but its effect is visible only millions of years ago. Evolution in living beings is possible only when they live in harmony with nature and keep struggling.
Criticism of Darwinism
Initially scientists considered Darwin's theory of natural selection to be more logical but later criticism began and many such errors were pointed out which even Darwin himself could not explain properly.
1. In Darwinism, more importance has been given to the subtle changes produced in the struggle for life. This theory has been completely unable to analyze how much use or importance these special characteristics and changes had in the situation before their full development.
2. Darwinism does not show the effect of reproduction and variation in somatic cells.
3. Darwinism was completely unable to throw any light regarding vestigial organs, although many vestigial organs are found in animals.
4. Darwinism was completely unable to throw light on the use and disuse of organs.
5. Darwinism was unable to explain the sudden changes in genes in any generation.
6. According to the Darwinian school of thought, useful changes are passed from one generation to the next through heredity. Many useless changes are also passed from one generation to the next through heredity, for example, the Irish elk became extinct forever because they were unable to protect themselves due to their useless huge horns.
7. Darwinism showed improvement in animals through selection, but was unable to explain why changes in organisms due to changes in the environment were not inherited by offspring.
Introduction to Darwin
Darwin was born on 12 February 1809, his father was a doctor. His father's name was Robert Waring Darwin. He was interested in natural things since childhood. He studied medicine and graduated from Cambridge University. At the age of only 22, he went on a world survey ship with the famous scientist Dr. Hans Low and surveyed the flora of many islands of Antarctica, the Galapagos Islands and the continents for 5 years.
He collected many important facts like fossils of animals and rocks etc. Before world conservation, he believed in particularism but later during his travel, his belief got focused on the hypothesis of biological evolution and a new hypothesis about the origin of organisms was awakened in his mind. After traveling the whole world, a hypothesis about the subject of geology was awakened in his mind.
They had discovered that the struggle for life among organisms leads to natural selection of those members of a species who are more capable than all other members of the species. In the same year they published this hypothesis under their joint names, which is known as Darwin's theory or Darwinism.
The new philosopher
It was liked a lot by contemporary scientists and it received more and more support. Darwinism was first published in 1859 and for about 40 years scientists had unwavering faith in it. This is known as the emotional period of Darwinism. In the early part of the 19th century, in 1900, scientists named Hugo de Vries of Holland, Tschermak of Austria and Correns of Germany, after re-discovering Mendel's principles of genetics, clarified that only the changes or variations based on genes are inherited.
Attempts were made to modify Darwinism on the basis of modern experiments, but these efforts led to the statement that new species of organisms are formed due to changes in the genes of previous species. Changes in genes are responsible for changes in the genetic characteristics of organisms. This change is called mutation . This statement is called neo-Darwinism .
Darwinism based on key facts
1. High rate of reproduction in organisms: Organisms have a natural desire to increase their family by producing offspring like themselves. For this, all species, whether they are animals or plants, have a tremendous capacity to produce offspring. For example, a fungus can produce 60-65 crore spores. An oyster lays 60 lakh eggs every year. Female Ascaris lays 2.7 crore eggs. If all the offspring survive and their number keeps increasing on an average from generation to generation, then one day the entire earth will be filled with these organisms. But this does not happen. Due to many reasons, eggs and newborns get destroyed and the number of organisms remains stable.
2. Struggle among animal species Despite the immense reproductive capacity of animal species, the number does not increase in geometric proportion, a balanced population is maintained. The main reason for this is the abundance of carnivorous animals, lack of favorable conditions and unfavorable environment etc. Members of many animal species die before becoming adults. Struggle for life Every organism has to struggle with other organisms to fulfill its needs. This struggle for life starts from the embryonic stage of every organism and continues throughout life.
The struggle for life is mainly of three types-
(a) Intraspecific struggle: Fierce struggle occurs among organisms of the same species due to similar needs, mainly for obtaining food, suitable habitat and selection of mate for sexual reproduction.
(b) Interspecific conflict: Organisms of different species struggle with each other to fulfil their survival needs and protection.
(c) Environmental Struggle : Organisms struggle for survival in different environmental conditions such as drought, flood, high wind speed, extreme heat and cold etc.